1// Copyright 2016 Amanieu d'Antras
2//
3// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
4// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
5// http://opensource.org/licenses/MIT>, at your option. This file may not be
6// copied, modified, or distributed except according to those terms.
7
8//! This library exposes a low-level API for creating your own efficient
9//! synchronization primitives.
10//!
11//! # The parking lot
12//!
13//! To keep synchronization primitives small, all thread queuing and suspending
14//! functionality is offloaded to the *parking lot*. The idea behind this is based
15//! on the Webkit [`WTF::ParkingLot`](https://webkit.org/blog/6161/locking-in-webkit/)
16//! class, which essentially consists of a hash table mapping of lock addresses
17//! to queues of parked (sleeping) threads. The Webkit parking lot was itself
18//! inspired by Linux [futexes](http://man7.org/linux/man-pages/man2/futex.2.html),
19//! but it is more powerful since it allows invoking callbacks while holding a
20//! queue lock.
21//!
22//! There are two main operations that can be performed on the parking lot:
23//!
24//! - *Parking* refers to suspending the thread while simultaneously enqueuing it
25//! on a queue keyed by some address.
26//! - *Unparking* refers to dequeuing a thread from a queue keyed by some address
27//! and resuming it.
28//!
29//! See the documentation of the individual functions for more details.
30//!
31//! # Building custom synchronization primitives
32//!
33//! Building custom synchronization primitives is very simple since the parking
34//! lot takes care of all the hard parts for you. A simple example for a
35//! custom primitive would be to integrate a `Mutex` inside another data type.
36//! Since a mutex only requires 2 bits, it can share space with other data.
37//! For example, one could create an `ArcMutex` type that combines the atomic
38//! reference count and the two mutex bits in the same atomic word.
39
40#![warn(missing_docs)]
41#![warn(rust_2018_idioms)]
42#![cfg_attr(
43 all(target_env = "sgx", target_vendor = "fortanix"),
44 feature(sgx_platform)
45)]
46#![cfg_attr(
47 all(
48 feature = "nightly",
49 target_family = "wasm",
50 target_feature = "atomics"
51 ),
52 feature(stdarch_wasm_atomic_wait)
53)]
54
55mod parking_lot;
56mod spinwait;
57mod thread_parker;
58mod util;
59mod word_lock;
60
61pub use self::parking_lot::deadlock;
62pub use self::parking_lot::{park, unpark_all, unpark_filter, unpark_one, unpark_requeue};
63pub use self::parking_lot::{
64 FilterOp, ParkResult, ParkToken, RequeueOp, UnparkResult, UnparkToken,
65};
66pub use self::parking_lot::{DEFAULT_PARK_TOKEN, DEFAULT_UNPARK_TOKEN};
67pub use self::spinwait::SpinWait;
68